This invention relates in general to tire changing equipment and more particularly to a machine for breaking large tires away from their rims.
Large trucks of the type used at mines and quarries as well as some earth moving equipment are often equipped with so-called giant tires which range up to nine feet in diameter. These tires when installed on their metal rims weigh over a ton each. Aside from being somewhat difficult to handle, these tires are extremely difficult to remove from the metal rims on which they are installed, at least by methods heretofore employed. Indeed, tha task is extremely burdensome and time consuming, often taking one man an entire work shift to change such a tire.
More specifically, most giant tires are of the tubeless variety and are installed on so-called five-piece rims. As the name implies, these rims have five basic components, namely, a rim base, a bead seat ring fitted over one side of the rim base, a flange at the side of the rim base opposite the bead seat ring, another flange on the bead seat ring, and a lock ring to hold the bead seat ring in place. The sidewalls of the tire at their inner margins have beads which tightly embrace tapered bead seats on the bead seat ring and the rim base adjacent to the flanges thereon to form air tight seals at those locations. After the tire has been in use for a short period of time, these seals are extremely difficult to break. Indeed, the rubber of the tire seems to almost bond to the metal of the rim at those locations.
The conventional procedure for breaking down a giant tire, that is for breaking the tire beads away from the tapered bead seats, is to lay the tire on its side and work around it step-by-step with a ram-type break-down tool. This tool consists of a relatively small clamp which grips the flange on the rim and forms an anchor against which a small pneumatic ram is positioned. The ram in turn carries a small contoured shoe which is forced into the space between the tire sidewall and the flange to move the bead down the taper of the bead seat and thereby break it away from the bead seat. Each entry of shoe into the space between the flange and tire sidewall dislodges only a small portion of the sidewall from the bead seat since the shoe is only about 3 inches wide, and as a result, the clamp must be moved around the rim and the procedure repeated at relatively close intervals. This is time consuming. Also, there is a tendency to use pry bars and sledge hammers on the rim to accelerate the procedure, and this results considerable rim damage, sometimes rendering the rim is impossible to reassemble.
Not only is the conventional procedure for changing giant tires a time consuming and burdensome operation, but it also can be quite dangerous for inattentive workers. Indeed, workers have been seriously injured and partially disabled as a result of having their fingers pinched between the sidewalls and rim flanges.